Dopamine depletion effects on cognitive flexibility as modulated by tDCS of the dlPFC

Background Recent evidence suggests that transcranial direct current stimulation (tDCS) may interact with the dopaminergic system to affect cognitive flexibility. Objective/hypotheses: We examined whether putative reduction of dopamine levels through the acute phenylalanine/tyrosine depletion (APTD) procedure and excitatory anodal tDCS of the dorsolateral prefrontal cortex (dlPFC) are causally related to cognitive flexibility as measured by task switching and reversal learning. Method A double-blind, sham-controlled, randomised trial was conducted to test the effects of combining anodal tDCS and depletion of catecholaminergic precursor tyrosine on cognitive flexibility. Results Anodal tDCS and tyrosine depletion had a significant effect on task switching, but not reversal learning. Whilst perseverative errors were significantly improved by anodal tDCS, the APTD impaired reaction times. Importantly, the combination of APTD and anodal tDCS resulted in cognitive performance which did not statistically differ to that of the control condition. Conclusions Our results suggest that the effects of tDCS on cognitive flexibility are modulated by dopaminergic tone

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Seismic stratigraphy and evolution of the Raggatt Basin, southern Kerguelen Plateau

Six major seismic stratigraphic sequences in the Raggatt Basin on the southern Kerguelen Plateau overlie a basement complex of Cretaceous or greater age. The complex includes dipping reflectors which were apparently folded and eroded before the Raggatt Basin developed. The seismic stratigraphic sequences include a basal unit F, which fills depressions in basement; a thick unit, E, which has a mounded upper surface (volcanic or carbonate mounds); a depression-filling unit, D; a thick unit C which is partly Middle to Late Eocene; and two post-Eocene units, A and B, which are relatively thin and more limited in areal extent than the underlying sequences. A mid or Late Cretaceous erosional episode was followed by subsidence and basin development, interrupted by major erosion in the mid Tertiary. Late Cenozoic sedimentation was affected by vigorous ocean currents

MAJOR EVOLUTIONARY PHASES OF A FORE-ARC BASIN OF THE ALEUTIAN TERRACE - RELATION TO NORTH PACIFIC TECTONIC EVENTS AND THE FORMATION OF THE ALEUTIAN SUBDUCTION COMPLEX

Combined geologic and seismic reflection data from the Atka Basin region of the Aleutian forearc show that the upper 2-3 km of slightly deformed sediment filling the\ud basin are probably of late Miocene to Holocene age. The depositional axis of the basin shifted arcward over time because of the progressive and differential rise of the\ud basin's outer ridge. Units filling the basin unconformably overlie and, along the edges of the basin, onlap beds of Oligocene age and older(?). The basal units of the basin fill are characterized by little variation in thickness, somewhat irregular internal reflectors, fault offsets, and possible wedge outs against units of Eocene(?) age. A fault\ud with at least 500 m of vertical displacement cuts the outer high of the forearc basin and displaces beds of the basin-filling series relative to those trenchward of the trenchslope break. The Atka Basin appears to have\ud formed in response to a combination of (1) initiation of trench-floor-filling turbidite deposition, in part derived from glacial marine sedimentation from mainland Alaska;\ud (2) an increased rate and normal component in Pacific plate subduction beneath the central Aleutian arc beginning in early Pliocene time; and (3) formation of a broad\ud and thick accretionary wedge that progressively uplifted the outer high of the Aleutian terrace

Polarity and timing-dependent effects of transcranial direct current stimulation in explicit motor learning

► Transcranial direct current stimulation (tDCS) modulates explicit sequence learning. ► Anodal tDCS applied during the task speeds motor learning. ► Anodal tDCS applied before the task slows motor learning. ► Cathodal tDCS slows the rate of learning in both cases